Abstract
A systematic numerical framework based on Integral Equations and Generalized Sheet Transition Conditions (IE-GSTCs) is presented in 2D to synthesize closed metasurface holograms and skins for creating electromagnetic illusions of specified objects and as a special case, to camouflaging them against their backgrounds. The versatile hologram surface is modeled using a zero-thickness sheet model of a generalized metasurface expressed in terms of its surface susceptibilities, which is further integrated into the GSTCs and the IE current-field propagation operators. To estimate the effectiveness of the illusions, the notion of a scene constructed by an observer is developed from first principles and a simple mathematical model, referred to as a Structured Field Observation (SFO), based on spatial Fourier transform is proposed. Using numerical examples, it is shown that to recreate the reference desired fields everywhere in space using a closed metasurface hologram/skin, an internal illumination must be applied inside the hologram, in addition to the applied external illumination fields. Finally, several numerical examples are presented for simple, angle-dependent and dynamic illusions. Finally, a dynamic camouflaged region of space, which can freely move inside a given complex scene without being detected by the observer is demonstrated.
Highlights
Electromagnetic (EM) invisibility has gathered an immense interest in the past two decades as a result of a rapid development in the general area of electromagnetic metamaterials
Two approaches are used in this paper: 1) a direct comparison of scattered or total fields at an observation position or a set of observation positions defined by a line or arc, and 2) a more sophisticated sampling of the field within an observation region allowing for the incorporation of a field of view and the directionality of the scattered and total field components
A systematic numerical framework based on IE-Generalized Sheet Transition Conditions (GSTCs) has been presented in 2D to synthesize closed metasurface holograms and skins for creating electromagnetic illusions of specified objects
Summary
Electromagnetic (EM) invisibility has gathered an immense interest in the past two decades as a result of a rapid development in the general area of electromagnetic metamaterials. Creating holograms naturally demands a versatile and a flexible surface that can be engineered to project myriad of illusions, including camouflage To realize such holograms, Electromagnetic Metasurfaces represent a powerful platform due to their complete control over the scattered fields with respect to both complex amplitude and polarization. 2) Electromagnetic Camouflage using a Metasurface Skin: consider an alternate scenario where the object is first removed from the reference scene as shown, so that the observer measures the fields corresponding to the background only in the presence of other possible scattering objects. The object while being physically present in the scene is still undetected by the observer, where it has effectively blended into the background, i.e. an electromagnetic camouflage Such a closed surface, as will be shown later, will be realized using an electromagnetic metasurface, and will be referred to as a Metasurface Skin. The objective here now is to synthesize these metasurfaces
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